Briton Paul Butler intends to upset the odds by beating Naoya Inoue to become the first undisputed bantamweight champion in half a century.

Japanese three-weight world champion Inoue, 29, holds the WBA (Super), WBC and IBF belts, and is unbeaten in 23 fights, with 20 knockouts.

“If I get the gameplan right, I believe I’ll win,” Butler, 34, told BBC Sport.

“It’s a tough fight. I’ve got to stay switched on.”

Inoue – nicknamed ‘The Monster’ – is second in Ring Magazine’s esteemed pound-for-pound rankings and will fight at home for the 20th time in his career.

“Inoue deserves his title as pound-for-pound king,” said Butler – a two-time world champion.

“Everyone knows what he does well. He puts people away and stops people.”

Butler, who was upgraded to WBO champion in May when John Riel Casimero was stripped of the belt, is a big underdog going into Tuesday’s fight.

But though he is under no illusions about the size of the task – describing Inoue as a “special” fighter – he says people are wrong to write him off.

“I’ve definitely earned the chance,” he said. “Inoue’s human, that is what he is.

“He’s got two arms, two legs. He’s no different to any other opponent.”

A disrupted journey meant it took Butler three days to travel to Japan, but he said he was “happy” to be fighting there, with long-time coach Joe Gallagher alongside him.

And after watching Inoue in his two fights with the legendary Nonito Donaire, Butler believes there are holes in his opponent’s defence he is capable of exploiting.

Inoue was hurt repeatedly in his first fight with Donaire in 2019, before blowing him away in two rounds in their rematch in 2022.

“If you’re looking for gaps, you only need to look at the first fight,” he said.

“There’s plenty to be seen, especially the first few rounds. Then in the mid to late rounds you can see a lot of gaps.

“I’m a little bit better than Donaire, fresher, and there’s not many miles on the clock with me.

“I believe that if I get the chance, I will exploit those gaps.”

Panamanian Enrique Pinder was the last undisputed bantamweight champion – in 1972.

There has never been an undisputed champion in the four-belt era, and Butler would be just the third Briton after Chantelle Cameron and Josh Taylor to achieve the feat.

“I can’t even explain what it would mean to me,” he said.

“It’s massive. It’s something I’ve worked for since I was a 10-year-old boy.

“I don’t think Inoue underestimates anyone… but if he has cut any corners and he has underestimated me, he’ll find out.”